Causes of reduction in vision (blurred vision, hazy vision, indistinct vision, dry eye) and eyestrain are known as near (reflex) triad. The near triad includes (1) reduction of accommodation, (2) reduction of pupillary response, and (3) convergence response abnormality. Reduction of accommodation is attributed to hypertonicity of the ciliary muscle or lens hardening. Reduction in pupillary response is caused by a decrease in pupillary constriction rate or decrease in response speed. Convergence response abnormality is attributed to an abnormal change of pupil position of both eyes. One of the known causes of dry eye is insufficient tear film formation on the corneal surface due to obstruction of meibomian glands.
In this connection, Patent Document 1 assigned to the common assignee of the present invention proposes a vision improving device that supplies steam to the eyes and its surroundings thereby to improve the function of accommodation muscles including ciliary muscle and improve the visual acuity of pseudomyopic eyes or aged eyes. The vision improving device is designed to release steam from its surface at a controlled temperature of 50° C. or lower thereby to recover the vision or reduce bleariness or blur in vision associated with dysfunction of accommodation muscles or accommodative spasm easily and effectively. Patent Document 1 describes the vision improving device as having effects on the improvement of declined accommodation, one of the near triad responses. The publication does not mention, however, whether the proposed vision improving device is effective in improving pupillary response and convergence response, the rest of the near reflex triad.    Patent Document 1 JP 2002-65714A